In most hollow needle tufting machines, as typified by Kile, U.S. Pat. No. 4,549,496 and Davis, at al., U.S. Pat. No. 5,588,383, each hollow needle is laterally spaced apart from the next needle by a distance of at least 2 inches and in some instances up to about 2 or 3 feet. This spacing has been necessary because of the complexity of the apparatus required to selectively feed one of the plurality of yarns for tufting by the hollow needle and then to remove the tufted yarn and replace it with another selected yarn to produce a change of color. A disadvantage of this spacing is that for hollow needles spaced on 2 inch centers, it is necessary to sew 20 lateral stitches in order to complete one row of tenth gauge spaced stitching before the backing fabric can be advanced and another row of stitching begun. For even finer gauge stitches of one-sixteenth gauge spacing, 32 lateral stitches are required before advancing to the next row. In this instance, even if the tufting machine is achieving about 900 stitches per minute, the stitch rate is only sufficient to tuft 30 rows of stitches in the backing fabric per minute. Since high speed tufting machines using standard needles can tuft 1,500 rows of stitches per minute, the hollow needle machines are at a considerable speed disadvantage. Accordingly, the need exists to design a hollow needle tufting apparatus where the needles may be compactly spaced thereby permitting a row of yarns to be completed in a smaller number of stitches. For instance, if hollow needles can be spaced every half inch, it will be possible to complete a row of stitches in only one-fourth the time that is required when the needles are spaced two inches apart. The result is that the tufting machine will be able to produce four times the amount of finished carpet in the same amount of time.
Due to the circular nature of the hollow needles, and the cutting mechanism utilized where a knife blade slides across an angled cutting surface at the end of the hollow needle, as described in Ingram U.S. Pat. No. 4,991,523, it is critical that the needle be properly aligned so that the knife blade makes uniform contact across the angled cutting surface. While truing the needle position when needles are spaced two inches apart laterally has been possible with some patience, when the needle spacing is reduced, frequently an adjustment to one needle will loosen an adjacent needle. Therefore, a mechanism is needed to precisely orient closely spaced needles without undue manual adjustment.
In addition to difficulties in properly orienting closely spaced needles, the penetration of backing fabric by closely spaced needles tends to drag the backing fabric downward resulting in yarn bights of uneven height and difficulties in implanting short yarn pile heights in the backing. The usual use of fingers extending from a backing support between needles is not practical in the case of hollow needle tufting apparatus due to the need to tuft a plurality of lateral stitches to create each row, which would drag tufted yarns across those needle fingers. Accordingly, an improved method of supporting backing fabric is needed.
In order to accomplish these and other objectives of the invention, an improved funnel assembly is provided with yarn spaced longitudinally fore and aft rather than annularly about the needle. The hollow needle itself is provided with a self aligning head so that the hollow needle is precisely set in a needle block with its angled cutting surface positioned to precisely cooperate with an associated knife.
An improved backing support plate is also provided to minimize the deflection of the backing fabric by the needles while still permitting lateral stitching.